"A lot of people up here have no patience for these guys," a naturalist at Denali had told me when I asked her about the two men. "Because there are people here who have stayed in that bus, and they had no problems. But you've got to have respect for the land, to learn it. The one thing you learn here is preparedness."

That's why people in Alaska study how to read wolf scat and the habits of bears. "Right here she knows you're not going to come any closer, and she's fine," a guide at Redoubt Bay had explained about a nearby mother bear with her cubs. "But go somewhere she doesn't expect you, and Bailey will most likely kill you."

One morning in Denali, a hiking guide had pointed out a poisonous plant McCand­less might have eaten by mistake. Then she showed me another plant, one, she said, that "would have kept him going to this day: Eskimo potatoes." (McCandless may have actually eaten the correct plant but mold on the seeds could have prevented his body from absorbing any nutrients.) To my eye they looked the same. I thought back to the maps I'd run my fingers along before coming here, many of the names opaque to me, others—Point Hope—sounding as if anxious visitors had tried, through invocation, to transform desolation into civilization. Some places seemed to combine prayers and warnings: Holy Cross, Elfin Cove, Cold Bay; Troublesome Creek, Moses Point, False Pass. Hours after I'd arrived in Anchorage, volcanic ash had drifted over from one of the Aleutian Islands, about a thousand miles away, closing down the airport—as if to say that all certainties were slamming shut and I was alone now in the realm of the possible.

Pico Iyer has written nine books. His most recent is The Open Road: The Global Journey of the Fourteenth Dalai Lama.

Editor's Note: A sentence in this article was corrected to clarify the geographic location of Alaska's easternmost Aleutian islands.